With "World News" broadcasts from San Francisco, we started a series to highlight efforts in this environmentally-friendly city to fight global warming.
We then decided to take a look at the impact each of us has -- as individucals -- on global warming, especially with respect to our "carbon footprint." The more carbon dioxide we put in the air, the greater our contribution to global warming.
We found two San Francisco residents and asked them if they believe most people think about their carbon footprint.
"Sadly, I don't think they do. I don't," said Daniel Oppenheim. "I'm delighted that there are environmentally-conscious people who are helping to do that. But currently, it's not a consideration for me."
Oppenheim, like most of us, has no idea how much he contributes to global warming. Driving is a big factor in carbon emissions, and he owns and loves to drive three vintage Land Rovers.
But there's a cost. The average American generates 20 tons of carbon dioxide or related gases a year. That's four to five times what people produce in other countries, because Americans produce far more greenhouse gases per capita than any other nation.
We found another San Francisco resident who is working to change his household's carbon emissions.
"We have now reduced our electricity bill by some 60 percent, and they were quite high," said Peter Boyer, who has placed 21 solar panels on his roof.
And on a long, sunny day they even contribute to the city's electricity supply. "Our meter will spin backward and we will be sending electricity into the grid and be credited for that," he said.
To reduce his carbon footprint, Boyer also uses energy-efficient appliances and special light bulbs.
He's also taking this attitude to the road, now driving a hybrid car that improved his gas mileage by 70 percent, which is important, as each gallon of gas that is burned sends 20 pounds of carbon dioxide into the air.
In comparison, Oppenheim's Land Rover produces 3,771 pounds of carbon in the atmosphere every year as Boyer's Prius adds 441 pounds.
And Oppenheim's home produces almost the same amount of carbon every year as Boyer's four person family.
Boyer believes one person can make a difference to the environment.
"Absolutely … but only in the company of many others," Boyer said. "You know, we got into this mess through millions of poor decisions, and we're only going to get out of it through millions of good decisions."